Lionel Messi and Luis Suarez were rested, and Ousmane Dembele returned from injury four months later. Valverde will have plenty of positives to draw from the match as a team of reserves competed with a Celta side packed with regular starters in La Liga.
It was mainly thanks to B-team forward Jose Arnaiz that Barcelona avoided defeat as they struggled in the rain against Celta. The 22-year-old Arsenal target buried a cross from Andre Gomes into the bottom corner with a crisp finish.
The hosts put the La Liga leaders under overwhelming pressure at times, knocking it around with pace. On the half hour, Pione Sisto equalised for the Galician side. Iago Aspas hit the bar and Sisto rifled into the roof of the net from a tight angle, past Jasper Cillessen.
It was the first time the visitors' back line had been pulled apart, and they were rarely troubled for the remainder of the fixture. The Catalans looked livelier after the break, with Sergio Busquets smashing the crossbar from 20 yards. It was the 28th time Barcelona had hit the frame of the goal this season, before Sergi Roberto made it 29 as he toe-poked an effort onto the outside of the post.
Denis Suarez missed a golden opportunity as he guided a volley wide with only Sergio Alvarez to beat and Emre Mor proved a manace as he flashed a low strike across goal and inches wide.
Ousmane Dembele was unable to make a noticeable impact as he came on with 20 minutes to play, playing in the slightly unfamiliar position of centre-forward. After a series late exchanges, the clash was brought to a close. Everything will be decided in the second leg of the Copa del Rey round of 16, at the Camp Nou.